Abstract
Abstract
Background
Ehrlichia canis
and canine
Babesia
spp. are widely distributed tick-borne pathogens of veterinary and One Health relevance. Contemporary nationwide data on canine exposure and associated determinants in Portugal are limited. This study aimed to estimate seropositivity proportions and explore epidemiological determinants of exposure to
E. canis
and
Babesia
spp. in clinically suspected dogs from Portugal over an 11-year period (2015–2025).
Methods
Serum samples from 2960 dogs collected between 2015 and 2025 were analysed using commercial enzyme-linked immunosorbent assay kits to detect immunoglobulin G antibodies to
E. canis
and
Babesia
spp. Associations with demographic and geographic variables were assessed using chi-square and Fisher’s exact tests. Univariable and multivariable logistic regression were used to identify potential risk factors (
P
2
, and the area under the receiver operating characteristic curve.
Results
Overall seropositivity was 4.0% (116/2,872) for
E. canis
and 12.0% (337/2,818) for
Babesia
spp. Borderline results accounted for 3.0% (88/2,960) and 4.8% (142/2,960), respectively.
E. canis
seropositivity varied significantly by Nomenclature of Territorial Units for Statistics level 2 region (
P
P
P
= 0.025). Age was associated with
E. canis
exposure (
P
= 0.014), with increased odds in dogs aged 6 to P
Babesia
spp. (
P
= 0.803), and sex and age were not significant predictors. Seropositivity to
Babesia
spp. was a risk factor for seropositivity to
E. canis
(OR = 3.6,
P
2
= 0.15; area under the curve = 0.71).
Conclusions
This study provides a nationwide, long-term retrospective assessment of serological exposure to
E. canis
and
Babesia
spp. among clinically suspect dogs in Portugal. Exposure to
E. canis
showed marked regional heterogeneity, particularly in southern Portugal, whereas
Babesia
spp. showed no significant regional association. Co-seropositivity, although uncommon, is consistent with shared tick-borne exposure pathways. These findings support risk-based tick control and continued surveillance within a One Health framework.